THE SPERMATOZOON 



143 



asexual swarmers or zoospores so common in the lower plants (Fi^^s. 

 70, 71). They differ in two respects from animal spermatozoa : first 

 in possessing not one but tw^o or several flagella ; second, in the fact 

 that these are attached as a rule not to the end of the cell, but on 

 the side. In the lower forms plastids are present in the form of 

 chromatophores, one 

 of which may be dif- 

 ferentiated into a red 

 *' eye-spot," as in 

 Volvox and Fiicus 

 (Figs. 57, 71, A), and 

 they may even contain 

 contractile vacuoles '^^ 



( Volvox ) ; but both 

 these structures are 

 wanting in the higher 

 forms. These con- 

 sist only of a nucleus 

 with a very small 

 amount of cytoplasm, 

 and have typically a 

 spiral form. In Chai^a, 

 where their structure 

 and development 

 have recently been 

 carefully studied by 

 Belajeff, the sperma- 

 tozoids have an elon- 

 gated spiral form with 

 two long flagella at- 

 tached near the 

 pointed end, which is 

 directed forward in 

 swimming (Fig. 70). 

 The main body of the 

 spermatozoid is oc- 

 cupied by a dense, 

 apparently homoge- 

 neous nucleus sur- 

 rounded by a very delicate layer of cytoplasm. Behind the nucleus lies 

 a granular mass of cytoplasm, forming one end of the cell, while in 

 front is a slender cytoplasmic tip to which the flagella are attached. 

 Nearly similar spermatozoids occur in the liverworts and mosses. In 

 the ferns and other pteridophytes a somewhat different type occurs 



Fig. 71.— Spermatozoids of plants. [./. B, C, E, after 

 Guignard; a F, after Strasburgek.] 



A. Of an alga {Fucus) ; a red chromatophore at the right 

 of the nucleus. B. Liverwort {Pcliia). C. Moss (>///./<'«//w). 

 D. Mars ilia. E. Fern. {Augtoptcris). F. Fern, Fhfi^opterts 

 (the nucleus dark). 



{Cf. Figs. 87. 88.) 



